Thin film polarizer, method of manufacturing the same, and polarizing plate and display device including the same

ABSTRACT

A method of manufacturing a thin film polarizer includes forming a film laminate by alternately bonding two or more non-oriented polymer films and two or more non-oriented polyvinyl alcohol-based films to each other using attractive force or an adhesive layer, orienting the film laminate so that the polyvinyl alcohol-based film has a thickness of 10 μm or less after the orienting of the film laminate, and separating the polymer films and the polyvinyl alcohol-based films of the oriented film laminate from each other.

This application is a National Stage application of PCT/KR2014/005185,filed on Jun. 12, 2014, which claims priority to Korean PatentApplication Nos. 10-2013-0069632, filed on Jun. 18, 2013, and10-2014-0067600 filed on Jun. 3, 2014, all of which are herebyincorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to a thin film polarizer, a method ofmanufacturing the same, and a polarizing plate and a display deviceincluding the thin film polarizer, and more particularly, to a thin filmpolarizer having a thickness of 10 μm or less, a method of manufacturingthe same, and a polarizing plate and a display device including the thinfilm polarizer.

BACKGROUND ART

Polarizers used in polarizing plates are optical devices enablingnatural light or optionally selected polarized light to be convertedinto polarized light having specific directionality and have been widelyused in display devices such as liquid crystal display devices andorganic light emitting devices (OLED). As polarizers used in displaydevices to date, polyvinyl alcohol (PVA)-based polarizing filmsincluding an iodine-based compound or dichroic dye and having amolecular chain aligned in a predetermined direction have generally beenused.

Polyvinyl alcohol-based polarizing films have commonly been manufacturedthrough a method of dying polyvinyl alcohol-based films with iodine or adichroic dye to then be oriented and crosslinked in a predetermineddirection. In this case, such an orientation process may be performedthrough a wet orientation process performed using a solution such as aboric acid aqueous solution or an iodine aqueous solution or through adry orientation process performed in an atmospheric environment, wherean orientation magnification is generally five or more times. However,in order to perform an orientation process in the manufacturing processaccording to the related art without the occurrence of breakage,polyvinyl alcohol-based films are required to have a thickness greaterthan 60 μm before the orientation process is performed. When polyvinylalcohol-based films have a thickness of 60 μm or less before theorientation process, a degree of swelling of polyvinyl alcohol-basedfilms may be increased, and a modulus of elasticity per unit area may beincreased due to a relatively reduced thickness such that breakages mayeasily occur in an orientation process.

On the other hand, in accordance with the recent trend for slimness indisplay devices, polarizing plates are also required to have arelatively reduced thickness. However, when polyvinyl alcohol-basedfilms having a thickness exceeding 60 μm before an orientation processas in the case of the related art are used, there may be limitations inreducing polarizer thicknesses. Therefore, research into themanufacturing of polarizers having a relatively reduced thickness hasbeen undertaken.

Korean Patent Laid-Open Publication No. 2010-0071998 discloses a methodof manufacturing a thin film polarizing plate using a stacked bodymanufactured by coating a base layer with a hydrophilic polymer layer (aPVA resin layer) or co-extruding a base layer formation material and ahydrophilic polymer layer formation material (a PVA resin). However, inthe case of the coating method or the coextrusion method in which a PVAlayer is coated or co-extruded on a base layer, since a polyvinylalcohol layer may not be easily separated from the base layer after theorientation process is performed and relatively great peel strength isrequired for the separation thereof, a problem in which the polyvinylalcohol layer is damaged or transformed during the separation process,or the like, may occur. As a result, physical optical properties such asa degree of polarization of manufactured polyvinyl alcohol polarizers,or the like, may be degraded. In addition, when the coating method orthe coextrusion method is used, since thin film polarizers aremanufactured in a scheme of dissolving a polyvinyl alcohol resin andthen extruding the same or producing a coating solution and applying thesame, physical properties of polyvinyl alcohol films manufacturedaccording to extrusion conditions, coating conditions, or unveilingconditions may be easily changed. Thus, difficulties in implementinguniform physical properties are present while physical properties ofconsequently manufactured polyvinyl alcohol films are deteriorated.

DISCLOSURE Technical Problem

Some embodiments of the present disclosure may provide a method ofmanufacturing a polarizer having a relatively reduced thickness whilehaving excellent optical properties so as to exhibit excellentproductivity.

Technical Solution

According to some embodiments of the present disclosure, a method ofmanufacturing a thin film polarizer may include forming a film laminateby alternately bonding two or more non-oriented polymer films and two ormore non-oriented polyvinyl alcohol-based films to each other usingattractive force or an adhesive layer, orienting the film laminate sothat the polyvinyl alcohol-based film has a thickness of 10 μm or lessafter the orienting of the film laminate, and separating the polymerfilms and the polyvinyl alcohol-based films of the oriented filmlaminate from each other.

The film laminate may include a first non-oriented polyvinylalcohol-based film, a first non-oriented polymer film bonded to thefirst non-oriented polyvinyl alcohol-based film, a second non-orientedpolyvinyl alcohol-based film bonded to the first non-oriented polymerfilm, and a second non-oriented polymer film stacked on the secondnon-oriented polyvinyl alcohol-based film.

The film laminate may include a first non-oriented polyvinylalcohol-based film, a first non-oriented polymer film bonded to thefirst non-oriented polyvinyl alcohol-based film, a second non-orientedpolyvinyl alcohol-based film bonded to the first non-oriented polymerfilm, a second non-oriented polymer film bonded to the secondnon-oriented polyvinyl alcohol-based film, and a third non-orientedpolyvinyl alcohol-based film bonded to the second non-oriented polymerfilm.

The non-oriented polymer film may be a polymer film having a maximumorientation magnification of five or more times, in detail, 5 to 15times, at a temperature of 20° C. to 85° C. As the non-oriented polymerfilm, for example, a high-density polyethylene film, a polyurethanefilm, a polypropylene film, a polyolefin film, an ester-based film, alow-density polyethylene film, high-density polyethylene and low-densitypolyethylene coextrusion films, a copolymer resin film containingethylene vinyl acetate in high-density polyethylene, an acrylic film, apolyethylene terephthalate film, a polyvinyl alcohol-based film, acellulose-based film, and the like, may be provided.

The orienting of the film laminate may be performed through dryorientation or wet orientation, and in the case of the wet orientation,the wet orientation may be performed in a boron aqueous solution havinga boron concentration ranging from 1 to 5 wt %.

The orienting of the film laminate may be performed at a temperature of20° C. to 85° C. at an orientation magnification of 5 to 15 times.

The method of manufacturing a thin film polarizer may further includedyeing the non-oriented polyvinyl alcohol-based film with at least oneof iodine and dichroic dye before the orienting of the film laminate.

Adhesion between the oriented polyvinyl alcohol-based film and theoriented polymer film after the orienting of the film laminate may be2N/2 cm or less, and the separating of the polymer film from thepolyvinyl alcohol-based film in the oriented film laminate may beperformed by applying 2N/2 cm or less of peel strength.

According to some embodiments of the present disclosure, a thin filmpolarizer manufactured through the method described above and having athickness of 10 μm or less, polarizer group transmittance of 40 to 45%,and a degree of polarization of 99% or more may be provided, and apolarizing plate and a display device including the same may beprovided.

Advantageous Effects

A thin film polarizer having a thickness of 10 μm or less may bemanufactured through a simplified process.

As described above, in a case in which an orientation process isperformed using a film laminate in which 2 or more polymer films and twoor more PVA films are stacked on each other, a breakage occurrence ratemay be significantly reduced even in the case of performing a highmagnification orientation so as to increase the degree of orientation ofa PVA polarizer. As a result, a thin film polarizer having excellentphysical optical properties may be manufactured.

In addition, according to the manufacturing method of the presentdisclosure, two or more thin film polarizers may be manufactured througha single process, whereby productivity may be excellent.

DESCRIPTION OF DRAWINGS

FIG. 1 is a drawing illustrating an adhesion measuring method using aTexture Analyzer;

FIG. 2 is a photograph illustrating a surface state of a film laminateafter orienting and drying the film laminate of Embodiment 1 of thepresent disclosure; and

FIG. 3 is a photograph illustrating a surface state of a film laminateafter orienting and drying the film laminate of Comparative Example 1 ofthe present disclosure.

BEST MODE FOR INVENTION

As a result of repeated research in order to manufacture a thinpolyvinyl alcohol-based polarizing film, the inventors of the presentdisclosure found that by using a stacked film formed by bonding anon-oriented polyvinyl alcohol-based film having a reduced thickness toone surface or both surfaces of a non-oriented polymer film, a polarizerhaving superior optical properties such as a high degree of polarizationor the like while having a reduced thickness of 10 μm or less may bemanufactured without the occurrence of breakages during a manufacturingprocess, and have filed the applications with Korean Patent ApplicationNo. 10-2012-0130576 (Title of Invention: Method of Manufacturing ThinFilm Polarizer, and Thin Film Polarizer and Polarizing Plate Using theSame) and 10-2012-0130577 (Title of Invention: Method of ManufacturingThin Film Polarizer, and Thin Film Polarizer and Polarizing Plate Usingthe Same).

However, in the case of these filed applications, there were limitationsin terms of the extent to which a breakage occurrence rate can bereduced. On the other hand, physical optical properties of a PVApolarizer is closely related to the degree of orientation of the PVAfilm, and as the higher the orientation magnification is, the higher thedegree of orientation of the PVA film is. Therefore, the presentdisclosure is provided as the results of repeated research undertaken bythe inventors of the present disclosure in order to manufacture a thinfilm polarizer having excellent physical optical properties andmanufacture a polarizer having a breakage occurrence rate lower thanthat in the case of the filed applications described above at the timeof orientation at a high multiplication.

Hereinafter, exemplary embodiments of the present disclosure will now bedescribed in detail with reference to the accompanying drawings. Thedisclosure may, however, be exemplified in many different forms andshould not be construed as being limited to the specific embodiments setforth herein. Rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the disclosure to those skilled in the art. In the drawings,the shapes and dimensions of elements may be exaggerated for clarity,and the same reference numerals will be used throughout to designate thesame or like elements.

A method of manufacturing a thin film polarizer according to anexemplary embodiment of the present disclosure may include forming afilm laminate by alternately bonding two or more non-oriented polymerfilms and two or more non-oriented polyvinyl alcohol-based films to eachother using attractive force or an adhesive layer, orienting the filmlaminate so that the polyvinyl alcohol-based film has a thickness of 10μm or less after an orientation process, and separating the polymerfilms and the polyvinyl alcohol-based films of the oriented filmlaminate from each other.

As described above, in the case of using the film laminate including thetwo or more polymer films and the two or more polyvinyl alcohol-basedfilms, as compared to the case in which one sheet of polymer film isused, a modulus of elasticity value per unit area applied to a polyvinylalcohol-based film may be lowered when tension is applied to the filmlaminate in an orientation process, and thus, a breakage occurrence ratemay be reduced. As a result, a high magnification orientation may bestably performed. In addition, in a case in which a thin film polarizeris manufactured using the method as above, at least two sheets ofpolyvinyl alcohol-based polarizers may be obtained through a singleprocess and productivity thereof may be improved.

Hereinafter, a method of manufacturing a thin film polarizer accordingto an exemplary embodiment of the present disclosure will be describedin further detail.

First, two or more non-oriented polymer films and two or morenon-oriented polyvinyl alcohol-based films may be alternately bonded viaattractive force or an adhesive layer to thus form a film laminate.

According to an exemplary embodiment of the present disclosure, the filmlaminate may be employed as long as it has a structure in which two ormore sheets of non-oriented polymer film and two or more sheets ofnon-oriented polyvinyl alcohol-based film are alternately disposed, andthe numbers of the non-oriented polymer films or the non-orientedpolyvinyl alcohol-based films are not particularly limited.

For example, the film laminate may have a structure including a firstnon-oriented polyvinyl alcohol-based film, a first non-oriented polymerfilm bonded to the first non-oriented polyvinyl alcohol-based film, asecond non-oriented polyvinyl alcohol-based film bonded to the firstnon-oriented polymer film, and a second non-oriented polymer filmstacked on the second non-oriented polyvinyl alcohol-based film, forexample, a structure of a non-oriented polyvinyl alcohol-based film/anon-oriented polymer film/a non-oriented polyvinyl alcohol-based film/anon-oriented polymer film.

Alternatively, the film laminate may also have a structure including afirst non-oriented polyvinyl alcohol-based film, a first non-orientedpolymer film bonded to the first non-oriented polyvinyl alcohol-basedfilm, a second non-oriented polyvinyl alcohol-based film bonded to thefirst non-oriented polymer film, a second non-oriented polymer filmbonded to the second non-oriented polyvinyl alcohol-based film, and athird non-oriented polyvinyl alcohol-based film bonded to the secondnon-oriented polymer film, for example, a structure of a non-orientedpolyvinyl alcohol-based film/a non-oriented polymer film/a non-orientedpolyvinyl alcohol-based film/a non-oriented polymer film/a non-orientedpolyvinyl alcohol-based film. In addition to such structures, a filmlaminate having a structure in which a further increased number ofpolymer films or polyvinyl alcohol-based films are stacked on each othermay also be used. Such a modification will also be included in the scopeof the present disclosure.

On the other hand, the non-oriented polymer film used in the filmlaminate of the present disclosure may be provided to prevent thepolyvinyl alcohol-based film from being broken in the orientationprocess and may be a polymer film having a maximum orientationmagnification of five or more times under a temperature of 20° C. to 85°C. In this case, the maximum orientation magnification refers to anorientation magnification immediately before breakage occurs. On theother hand, the above-mentioned orientation may refer to a dryorientation process or a wet orientation process. In the case of the wetorientation process, concentration of boron may indicate a maximumorientation magnification in a case in which the orientation process isperformed using a boric acid aqueous solution having concentration ofboron of 1.0 to 5 weight %.

As such a polymer film, for example, a high-density polyethylene film, apolyurethane film, a polypropylene film, a polyolefin film, anester-based film, a low-density polyethylene film, high-densitypolyethylene and low-density polyethylene co-extrusion films, acopolymer resin film in which ethylene vinyl acetate is contained inhigh-density polyethylene, an acrylic film, a polyethylene terephthalatefilm, a polyvinyl alcohol-based film, a cellulose-based film, or thelike may be used, but the present disclosure is not limited thereto.

On the other hand, in the case of the present disclosure, two or morepolymer films are used, and in this case, the polymer films, forexample, the first non-oriented polymer film, the second non-orientedpolymer film, and the like, may be the same polymer film or may also bedifferent polymer films.

On the other hand, the non-oriented polymer film used in the presentdisclosure may have a thickness of around 20 μm to 100 μm, in detail,around 30 μm to 80 μm, in further detail, around 40 μm to 60 μm. Whenthe thickness of the non-oriented polymer film is less than 20 μm, sincethe polymer film may not sufficiently support the polyvinylalcohol-based film in the orientation process of the film laminate,breakage or the like may occur. When the thickness of the non-orientedpolymer film exceeds 100 μm, the orientation properties of the filmlaminate may be deteriorated, and free width contraction at the time ofdrying the polyvinyl alcohol-based film may be disturbed such thatphysical optical properties of a finally obtained polarizer may bedegraded.

In addition, a glass transition temperature of the non-oriented polymerfilm may be lower than that of the polyvinyl alcohol-based film, and forexample, may range from around 20° C. to 60° C., in further detail,around 30° C. to 60° C. Considering that a glass transition temperatureof the polyvinyl alcohol-based film is generally in a range of around70° C. to 80° C., when the glass transition temperature of the polymerfilm satisfies such numerical range, the polymer film may haverelatively softer characteristics under the orientation temperatureconditions. As a result thereof, orientation characteristics of thepolyvinyl alcohol-based film may be further improved. However, when theglass transition temperature is excessively low, since breakage mayoccur at the time of orientation at a high magnification, the glasstransition temperature of the polymer film may be 20° C. or higher. Onthe other hand, the glass transition temperature may be measured using adifferential scanning calorimeter (DSC). For example, when a sample ofabout 10 mg is sealed in a fan for a DSC only and is heated under apredetermined temperature rising condition, an absorption heat amountand a calorific value generated while a phase change occurs may bemeasured on a temperature thereof to measure the glass transitiontemperature thereby.

In addition, in the case of the non-oriented polymer film, a modulus ofelasticity thereof at a room temperature (25° C.) may range from around200 MPa to 1500 MPa, in detail, from around 350 MPa to 1300 MPa. Whenthe modulus of elasticity of the polymer film exceeds 1500 MPa, a highmagnification orientation may be difficult to be implemented, and whenthe modulus of elasticity of the polymer film is less than 200 MPa,breakage may occur during the orientation process. In this case, themodulus of elasticity refers to a value obtained by measuring stress perarea, based on strain provided by fixing both ends of a sample preparedaccording to JIS-K6251-1 standards and then applying force thereto in adirection perpendicular with respect to a thickness direction of a film.As a measurement device, for example, a Universal Testing Machine(Zwick/Roell Z010 UTM) or the like may be used.

In addition, in the case of the non-oriented polymer film, force atbreak point thereof at a room temperature (25° C.) may range from around5N to 40N, in detail, from around 10N to 30N. In this case, the force atbreak point refers to strain obtained at a point in time at which a filmis broken by fixing both ends of a sample and then applying strainthereto in a direction perpendicular with respect to a thicknessdirection of the film, and for example, may be measured using aUniversal Testing Machine (Zwick/Roell Z010 UTM) or the like. When theforce at break point of the non-oriented polymer film exceeds suchnumerical ranges, a high magnification orientation may be difficult tobe implemented or breakage may occur during an orientation process.

Subsequently, a non-oriented polyvinyl alcohol-based film interposedbetween the non-oriented polymer films may have a thickness of around 10to 60 μm, in detail, around 10 to 40 μm. In a case in which thethickness of the non-oriented polyvinyl alcohol-based film exceeds 60μm, a thickness of 10 μm or less may not be easily obtained even afterthe orientation process, and in a case in which the thickness thereof isless than 10 μm, breakage may easily occur during the orientationprocess.

On the other hand, the non-oriented polyvinyl alcohol-based film mayhave a degree of polymerization of around 1,000 to 10,000, in detail,around 1,500 to 5,000, but is not limited thereto. When the degree ofpolymerization satisfies such a range, a molecule movement may befacilitated, and molecules may be smoothly mixed with iodine, dichroicdye or the like.

Further, as the non-oriented polyvinyl alcohol-based film according toan exemplary embodiment of the present disclosure, polyvinylalcohol-based films for sale in the market may be used, and for example,PS30, PE30, PE60 by Kuraray, M2000, M3000, M6000 by Nippon Gohsei, orthe like may be used.

On the other hand, in the case of the present disclosure, two or morenon-oriented polyvinyl alcohol-based films may be used, and in thiscase, the plurality of non-oriented polyvinyl alcohol-based films, forexample, the first non-oriented polyvinyl alcohol-based film, the secondnon-oriented polyvinyl alcohol-based film, and the third non-orientedpolyvinyl alcohol-based film may have the degrees of polarization,compositions, or the like, the same as or different from each other.

On the other hand, according to an exemplary embodiment of the presentdisclosure, the non-oriented polyvinyl alcohol-based film may be a filmin a state in which it is dyed with iodine and/or dichroic dye. Infurther detail, the non-oriented polyvinyl alcohol-based film may be afilm having been subjected to a swelling process and the dyeing process.

To this end, before orienting the film laminate, a process of dyeing thenon-oriented polyvinyl alcohol-based film with iodine and/or dichroicdye may be further performed, and in further detail, processes ofswelling the non-oriented polyvinyl alcohol-based film and dyeing theswelled non-oriented polyvinyl alcohol-based film with iodine and/ordichroic dye may be further carried out.

In this case, the process of swelling the non-oriented polyvinylalcohol-based film may be performed to promote the iodine and/ordichroic dye to be absorbed into and spread on the polyvinylalcohol-based film and to improve orientation properties of thepolyvinyl alcohol-based film. For example, the swelling process may beperformed by dipping the non-oriented polyvinyl alcohol-based film inpure water of 25° C. to 30° C. for 5 to 30 seconds, in detail, for 10 to20 seconds, but is not limited thereto. In addition, the swellingprocess may be performed such that the degree of swelling of thenon-oriented polyvinyl alcohol-based film may be in a range of around36% to 44%, in detail, around 38% to 42%. When the degree of swelling ofthe non-oriented polyvinyl alcohol-based film satisfies such numericalranges, optical properties of a finally obtained thin film polarizer,such as a degree of polarization or the like, may be relativelyexcellent. On the other hand, the degree of swelling may be calculatedand represented by {(Weight of polyvinyl alcohol-based film afterswelling−Weight of polyvinyl alcohol-based film before swelling)/Weightof polyvinyl alcohol-based film before swelling}×100.

Further, the dyeing process may be performed by dipping and impregnatingthe non-oriented polyvinyl alcohol-based film in a dyeing tub of adyeing solution containing iodine and/or dichroic dye or coating thepolyvinyl alcohol-based film with a dyeing solution containing iodineand/or dichroic dye. In this case, as a solvent of the dyeing solution,although water may be generally used, an organic solvent havingcompatibility with water may also be mixed with water. On the otherhand, the content of iodine and/or dichroic dye in the dyeing solutionmay range from 0.06 parts by weight to 0.25 parts by weight with respectto 100 parts by weight of a solvent. Furthermore, the dyeing solutionmay further contain a supplemental agent to improve dyeing efficiency inaddition to iodine and/or dichroic dye. As the supplemental agent, aniodized compound such as potassium iodide, lithium iodide, sodiumiodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, bariumiodide, calcium iodide, tin iodide, titan iodide, and mixtures thereof,may be used. In this case, the content of the supplemental agent mayrange from around 0.3 parts by weight to 2.5 parts by weight withrespect to 100 parts by weight of a solvent, and in detail, a weightratio of iodine to iodine may range from around 1:5 to 1:10. On theother hand, the dyeing process may be performed at a temperature ofabout 25° C. to 40° C., and the impregnation process time thereof in thedyeing tub may be around 30 to 120 seconds, but the present disclosureis not limited thereto.

According to an exemplary embodiment of the present disclosure, a dyeingconcentration of the polyvinyl alcohol-based film may be adjusteddepending on a layout position of the polyvinyl alcohol-based film inthe film laminate. For example, a dyeing concentration of the polyvinylalcohol-based film disposed between the polymer films and a dyeingconcentration of the polyvinyl alcohol-based film disposed on anexternal surface of the film laminate may be the same as or differentfrom each other.

As in the present disclosure, in a case in which two or more polymerfilms and two or more non-oriented polyvinyl alcohol-based films arestacked on each other to form a film laminate, the degree of orientationof a polyvinyl alcohol-based film disposed between the polymer films(for example, the second polyvinyl alcohol-based film) may be somewhatdeteriorated as compared to that of a polyvinyl alcohol-based filmdisposed on the external surface of the film laminate (for example, thefirst polyvinyl alcohol-based film and/or the third polyvinylalcohol-based film). For example, a level of strain applied to thepolyvinyl alcohol-based film disposed between the polymer films at thetime of orientation may be relatively low as compared to that of thepolyvinyl alcohol-based film disposed on the external surface of thefilm laminate. Further, an extent to which boron is absorbed or diffusedat the time of impregnation in a boron aqueous solution may also berelatively small in the polyvinyl alcohol-based film disposed betweenthe polymer films, as compared to that of the polyvinyl alcohol-basedfilm disposed on the external surface of the film laminate, such that adegree of cross-linking thereof may be reduced. Therefore, in order toobtain uniform physical optical properties of a finally obtainedpolarizer, concentrations of dyeing solutions of the polyvinylalcohol-based film disposed between the polymer films and the polyvinylalcohol-based film disposed on the external surface of the film laminatemay be adjusted to be different from each other. Alternatively, theconcentrations of dyeing solutions of the polyvinyl alcohol-based filmdisposed between the polymer films and the polyvinyl alcohol-based filmdisposed on the external surface of the film laminate may also beidentical to each other so as to obtain two or more types of polarizerhaving different physical optical properties through a single process.In this case, since in the case of a polarizer having a relatively loworientation degree, the degree of polarization thereof is somewhatdeteriorated, while the transmittance thereof is relativelysignificantly high, the polarizer may be usefully used for an organiclight emitting device and the like. In addition, in the case of a PVApolarizer having a relatively high orientation degree, the polarizer maybe usefully used for a liquid crystal display device (LCD) or the likerequiring a relatively high degree of polarization. According toexperimental results of the inventors, in a case in which theconcentrations of dyeing solutions are the same as each other, filmgroup transmittance of the polyvinyl alcohol-based film disposed betweenthe polymer films and the polyvinyl alcohol-based film disposed on theexternal surface of the film laminate may be in a range of around 0.3%to 2.0%, and the degree of polarization thereof may be in a range ofaround 0.003% to 0.04% according to orientation conditions.

On the other hand, the film laminate according to an exemplaryembodiment may be manufactured by alternately bonding the non-orientedpolymer films and the non-oriented polyvinyl alcohol-based films to eachother via an adhesive or by alternately stacking the non-orientedpolymer films and the non-oriented polyvinyl alcohol-based films withouta separate medium material.

When the non-oriented polymer film and the non-oriented polyvinylalcohol-based film are bonded to each other using attractive force,surface treatment may be performed on one surface or both surfaces ofthe non-oriented polymer film or the polyvinyl alcohol-based film inorder to control adhesion. In this case, the surface treatment may becarried out through commonly known various methods, for example, coronaprocessing, plasma processing, surface modification processing using astrong alkali aqueous solution such as NaOH or KOH, or the like.

In a case in which the non-oriented polymer film and the non-orientedpolyvinyl alcohol-based film are bonded to each other, a thickness of anadhesive layer before an orientation process may be in a range of around20 nm to 4000 nm, in detail, around 20 nm to 1000 nm, in further detail,around 20 nm to 500 nm. A thickness of the adhesive layer after theorientation process of the film laminate may be in a range of around 10nm to 1000 nm, in detail, around 10 nm to 500 nm, in further detail,around 10 nm to 200 nm. When the thicknesses of the adhesive layerbefore and after the orientation process of the film laminate satisfythe ranges described above, delamination of the polyvinyl alcohol-basedfilm after the orientation process and a drying process may befacilitated without damage thereto.

A material of the adhesive is not particularly limited and variouscommonly known adhesives may be used without limitation. For example,the adhesive layer may be formed using a water-based adhesive or anultraviolet curable adhesive.

In further detail, the adhesive layer may be formed using a water-basedadhesive containing one or more selected from a group consisting of apolyvinyl alcohol-based resin, an acrylic resin, and a vinylacetate-based resin.

Alternatively, the adhesive layer may be formed using a water-basedadhesive containing an acrylic group and hydroxyl group-containingpolyvinyl alcohol-based resin. Here, the acrylic group and hydroxylgroup-containing polyvinyl alcohol-based resin may have a degree ofpolymerization of around 500 to 1800.

Alternatively, the adhesive layer may be formed using a water-basedadhesive including an amine-based metal compound crosslinking agent anda polyvinyl alcohol-based resin containing an acetoacetyl group. In moredetail, the adhesive may be an aqueous solution containing 100 parts byweight of the polyvinyl alcohol-based resin containing an acetoacetylgroup and 1 to 50 parts by weight of the amine-based metal compoundcrosslinking agent.

Here, although a degree of polymerization and a degree of saponificationof the polyvinyl alcohol-based resin are not particularly limited aslong as the polyvinyl alcohol-based resin only includes an acetoacetylgroup, the degree of polymerization thereof may be 200 to 4,000, and thedegree of saponification thereof may be 70 mol % to 99.9 mol %. In thiscase, the polyvinyl alcohol-based resin may include the acetoacetylgroup of 0.1 to 30 mol %. The action thereof with the amine-based metalcompound crosslinking agent may be smooth within the range describedabove, and water resistance of a targeted adhesive may be sufficientlysignificant.

The amine-based metal compound crosslinking agent is a water-solublecrosslinking agent having a functional group having reactivity with thepolyvinyl alcohol-based resin, and may have a metal mixture formcontaining an amine-based ligand. As a metal available for use therein,a transition metal such as zirconium (Zr), titanium (Ti), hafnium (Hf),tungsten (W), iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru),osmium (Os), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt),or the like may be used. As a ligand combined with a central metal, anyligand may be used, as long as it includes one or more amine groupformed of a material such as a primary amine, a secondary amine(diamine), a tertiary amine, ammonium hydroxide, or the like.

In addition, in the case of such an adhesive, a content of a solid ofthe polyvinyl alcohol-based resin including the acetoacetyl group may bewithin a range of about 1 to 10 weight %. When the solid content of thepolyvinyl alcohol-based resin is less than 1 weight %, since waterresistance thereof may not be sufficiently secured, an effect ofreducing the occurrence of breakage in the orientation process may berelatively low. When the solid content of the polyvinyl alcohol-basedresin exceeds 10 weight %, users' working power may be weakened, and atthe time of performing a separation process, a surface of the polyvinylalcohol-based film may be damaged.

A pH of the adhesive may be in a range of around 4.5 to 9. When the PHof the adhesive satisfies the numerical range described above, storageproperties and durability in a high moisture environment may be furtherimproved.

On the other hand, a pH of the adhesive may be adjusted through a methodof including an acid in an aqueous solution, and in this case, as acidused to adjust the pH thereof, strong acid and weak acid may both beused. For example, nitric acid, hydrochloric acid, sulfuric acid, aceticacid, or the like may be used.

On the other hand, a thickness of the adhesive layer formed using theadhesive as described above may be in a range of around 80 nm to 200 nm,in detail, around 80 nm to 150 nm, before the orientation process, andmay be in a range of around 10 nm to 100 nm, in detail, around 10 nm to80 nm, after the orientation process of the film laminate. When thethickness of the adhesive layer satisfy the ranges described above,adhesion between a base film and the polyvinyl alcohol-based film may bemaintained at an appropriate level such that a breakage occurrence rateat an orientation process may be lowered and damage to a polarizersurface may be significantly reduced at the time of the occurrence ofdelamination.

In the case of the adhesive described above, a crosslinking reaction mayoccur between the amine-based metal compound and the acetoacetyl groupof the polyvinyl alcohol-based resin such that water resistance of theadhesive layer after a curing process may be relatively high. Therefore,when the polymer film and the polyvinyl alcohol-based film are stackedusing the adhesive, a phenomenon in which the adhesive dissolves inwater may be significantly reduced so as to be more usefully used in thewet orientation process.

On the other hand, the adhesive layer may also be formed using anultraviolet curable adhesive including, for example, a first epoxycompound in which a glass transition temperature of a homopolymer is120° C. or higher, a second epoxy compound in which a glass transitiontemperature of a homopolymer is 60° C. or less, and a cationicphotopolymerization initiator. In detail, the ultraviolet curableadhesive may include 100 parts by weight of the first epoxy compound inwhich a glass transition temperature of a homopolymer is 120° C. orhigher, 30 to 100 parts by weight of the second epoxy compound in whicha glass transition temperature of a homopolymer is 60° C. or less, and0.5 to 20 parts by weight of the cationic photopolymerization initiator

In the present disclosure, the epoxy compound may refer to a compound inwhich one or more epoxy groups are contained in a molecule, in detail, acompound in which two or more epoxy groups are contained in a molecule,and may refer to a concept including a monomer, a polymer, or all ofcompounds of a resin form. In more detail, the epoxy compound accordingto an exemplary embodiment of the present disclosure may have the formof a resin.

On the other hand, as the first epoxy compound, any epoxy compound maybe used without particular limitations as long as it is an epoxycompound in which a glass transition temperature of a homopolymer is120° C. or higher. For example, an aromatic epoxy and/or an alicyclicepoxy compound in which the glass transition temperature of ahomopolymer is 120° C. or higher may be used as the first epoxy compoundof the present disclosure. As a detailed example of the epoxy compoundin which the glass transition temperature of a homopolymer is 120° C. orhigher, 3,4-epoxycyclohexylmethyl-3,4′-epoxycyclohexanecarboxylate,vinylcyclohexene dioxide dicyclopentadiene dioxide, bis epoxycyclopentyl ether, a bisphenol A-based epoxy compound, a bisphenolF-based epoxy compound, and the like, may be provided. In furtherdetail, as the first epoxy compound, an epoxy compound in which theglass transition temperature of a homopolymer is within a range ofaround 120° C. to 200° C. may be used.

As the second epoxy compound, any epoxy compound may be used withoutparticular limitations as long as it is an epoxy compound in which theglass transition temperature of a homopolymer is 60° C. or less. Forexample, as the second epoxy compound, an alicyclic epoxy compound, analiphatic epoxy compound, and the like, may be used.

In this case, as the alicyclic epoxy compound, a 2-functional epoxycompound, for example, a compound having two epoxy groups may be used.In further detail, a compound in which two epoxy groups are bothalicyclic epoxy groups may be used, but is not limited thereto.

As the aliphatic epoxy compound, an epoxy compound having an aliphaticepoxy group other than an alicyclic epoxy group may be used, by way ofexample. For example, polyglycidyl ether of aliphatic polyhydricalcohol; a polyglycidyl ether of alkylene oxide addition product withaliphatic polyhydric alcohol; polyglycidyl ether of polyester polyol ofaliphatic polyhydric alcohol and aliphatic polyhydric carboxylic acid;polyglycidyl ether of aliphatic polyhydric carboxylic acid; polyglycidylether of polyester polycarboxylic acid of aliphatic polyhydric alcoholand aliphatic polyhydric carboxylic acid; a dimer, an oligomer, or apolymer obtained through vinyl polymerization of glycidyl acrylate orglycidyl methacrylate; or an oligomer or a polymer obtained throughvinyl polymerization of a vinyl-based monomer different from glycidylacrylate or glycidyl methacrylate may be used. In detail, polyglycidylether of aliphatic polyhydric alcohol or alkylene oxide addition productthereof may be used, but the present disclosure is not limited thereto.

In this case, as the aliphatic polyhydric alcohol, for example,aliphatic polyhydric alcohols having a carbon number range of 2 to 20, 2to 16, 2 to 12, 2 to 8, or 2 to 4 may be provided by way of example. Forexample, aliphatic diols such as ethylene glycol, 1,2-propanediol,1,3-propanediol, 2-methyl-1,3-propanediol,2-butyl-2-ethyl-1,3-propanediol, 1,4-butanediol, neopentyl glycol,3-methyl-2,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol,3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol,2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol,3,5-heptanediol, 1,8-octanediol, 2-methyl-1,8-octanediol,1,9-nonanediol, and 1,10-decanediol; alicyclic diols such ascyclohexanedimethanol, cyclohexanediol, hydrogenated bisphenol A, andhydrogenated bisphenol F; trimethylolethane, trimethylolpropane,hexitols, pentitols, glycerine, polyglycerine, pentaerythritol,dipentaerythritol, tetramethylolpropane, and the like, may be used.

In addition, as the alkylene oxide, alkylene oxide having a carbonnumber range of 1 to 20, 1 to 16, 1 to 12, 1 to 8, or 1 to 4 may beprovided by way of example. For example, ethyleneoxide, propyleneoxide,butyleneoxide, or the like, may be used.

In addition, as examples of the aliphatic polyhydric carboxylic acid,oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid,pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanoic acid,2-methylsuccinic acid, 2-methyladipic acid, 3-methyladipic acid,3-methylpentanoic acid, 2-methyloctanoic acid, 3,8-dimethyl decanoicacid, 3,7-dimethyl decanoic acid, 1,20-eicosamethylenedicarboxylic acid,1,2-cyclopentanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid,1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid,1,4-cyclohexanedicarboxylic acid, 1,4-dicarboxylmethylenecyclohexane,1,2,3-propanetricarboxylic acid, 1,2,3,4-butanetetracarboxylic acid,1,2,3,4-cyclobutanetetracarboxylic acid, and the like, may be provided.However, the present disclosure is not limited thereto.

In detail, the second epoxy compound of the present disclosure maycontain one or more glycidyl ether groups. For example, as the secondepoxy compound according to an exemplary embodiment of the presentdisclosure, one or more selected from a group consisting of1,4-cyclohexanedimethanol diglycidyl ether, 1,4-butanediol diglycidylether, 1,6-hexanediol diglycidyl ether, neopentyl diglycidyl ether,resorcinol diglycidyl ether, diethylene glycol diglycidyl ether,ethylene glycol diglycidyl ether, trimethylolpropanetriglycidyl ether,n-butyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidylether, and o-cresyl glycidyl ether may be used.

The second epoxy compound in which the glass transition temperature of ahomopolymer ranges from around 0° C. to 60° C. may be used.

Meanwhile, in further detail, as the epoxy compound according to anexemplary embodiment of the present disclosure, a combination of a firstepoxy compound containing one or more epoxidized aliphatic ring groupsand a second epoxy compound containing one or more glycidyl ether groupsmay be used, but the present disclosure is not limited thereto.

After forming the film laminate as described above, the film laminatemay be subjected to an orientation process. Here, the orientationprocess may be performed so that the polyvinyl alcohol-based film mayhave a thickness of 10 μm or less, in detail, may have a thickness ofaround 1 μm to 10 μm, around 3 μm to 10 μm, or around 1 μm to 5 μm.

On the other hand, although orientation conditions according to anexemplary embodiment of the present disclosure are not particularlylimited, the orientation process may be performed, for example, at atemperature of 20° C. to 85° C. and at an orientation magnification of 5to 15 times, in further detail, at a temperature of 40° C. to 80° C. andat an orientation magnification of 5 to 12 times.

In this case, the orientation process may be performed through wetorientation or dry orientation. However, since in the case of the wetorientation process, surface adhesion of the non-oriented polymer filmand the polyvinyl alcohol-based film may be increased as compared tothat in the dry orientation process, the wet orientation process may beperformed in that it is stably performed without a separate adhesiveunit. The wet orientation process may be performed in a boron aqueoussolution. Here, boron concentration of the boron aqueous solution mayrange from around 1.0 to 5.0 wt %.

In a case in which the orientation process is performed in the boronaqueous solution as described above, a breakage occurrence rate of a PVAfilm may be reduced due to boron crosslinking such that stability in theprocess may be increased and the occurrence of wrinkles in the PVA filmoccurring during a wet process may be suppressed. In addition, theorientation process may also be performed at a relatively lowtemperature as compared to that in the case of a dry orientationprocess.

On the other hand, a process of manufacturing a polarizing element maygenerally include a washing process, a swelling process, a dyeingprocess, a cleaning process, an orientation process, a complementaryprocess, a drying process, and the like, but in the case of the presentdisclosure, the cleaning and orientation processes may be performedusing a boric acid aqueous solution. In detail, in the case of thecleaning process, the concentration of boron may be within a range ofaround 0.1 to 2.5 wt %, or in further detail, around 0.5 to 2.0 wt %,and in the case of the orientation process, the concentration of boronmay be within a range of around 1.0 to 5.0 wt %, or in further detail,around 1.5 to 4.5 wt %.

On the other hand, after the orientation process of the film laminate,adhesion between the oriented polyvinyl alcohol-based film and theoriented polymer film may be 2N/2 cm or less, in detail, in a range ofaround 0.1 to 2N/2 cm, in further detail, around 0.1 to 1N/2 cm. Whenthe adhesion between the oriented polyvinyl alcohol-based film and theoriented polymer film satisfies the range described above, damage to asurface may be significantly reduced in a separation process. Accordingto the manufacturing method of the present disclosure, in a case inwhich an adhesive layer is formed between the polyvinyl alcohol-basedfilm and the polymer film, since the adhesive layer as well as thepolyvinyl alcohol-based film is oriented in the orientation process, athickness of the adhesive layer may be reduced to a level of 10 to 50%as compared to the case before the orientation process. As a result, theadhesion between the polyvinyl alcohol-based film and the polymer filmmay be lowered to 2N/2 cm or less, such that the separation process maybe facilitated. In this case, the adhesive force may be measured whensamples, for example, films having a length of 2 cm, are adhered, and adetailed measuring method is illustrated in FIG. 1. In the presentdisclosure, the adhesive force between the films indicates a magnitudeof peel strength measured when separating a polyvinyl alcohol film Afrom a polymer film B by applying force in a direction perpendicularwith respect to a surface direction of the film laminate after fixingthe polyvinyl alcohol film A of the film laminate using a sample holderH, as illustrated in FIG. 1. In this case, as the measuring device, aTexture Analyzer (TA-XT Plus) by Stable Micro Systems was used.

After the film laminate is oriented as described above, the orientedfilm laminate may further be subjected to a drying process as needed. Inthis case, the drying process may be performed at a temperature ofaround 20° C. to 100° C., or in further detail, around 40 to 90° C., for1 to 10 minutes. The drying process may prevent a PVA polarizer frombeing deteriorated in physical properties due to moisture during apolarizing plate manufacturing process, through removal of moisture froma PVA surface and inside, and may induce shrinkage in a width directionof the oriented polyvinyl alcohol film to be smoothly performed duringthe drying process so as to increase directivity of a dyed bodyincluding polyvinyl alcohol and iodine and thus improve a degree ofpolarization of the polarizer.

Subsequently, the polymer film and the polyvinyl alcohol-based film ofthe oriented film laminate may be separated from each other. In thepresent disclosure, the separation process may be carried out through amethod of applying a relatively low level of peel strength to thepolyvinyl alcohol-based film such that both films are detached from eachother. In this case, the peel strength may be 2N/2 cm or less, and forexample, may be in a range of around 0.1 to 2N/2 cm, or in furtherdetail, around 0.1 to 1N/2 cm. In the case of the present disclosure asdescribed above, since peel strength required at the time of separatingthe polyvinyl alcohol-based film from the polymer film is relativelyvery weak as compared to the case in which stacking is performed througha coating method or a co-extrusion method, both films may be easilyseparated from each other without a separate process and without usingseparate devices, and damage to the polyvinyl alcohol-based film may besignificantly reduced in the separation process such that significantlyexcellent optical performance may be exhibited.

On the other hand, the method of manufacturing a thin film polarizeraccording to an exemplary embodiment of the present disclosure may beperformed through a commonly known sheet-to-sheet process, asheet-to-roll process, or roll-to-roll process, or the like. Here, thesheet-to-sheet process may be performed through a method of using asheet-fed type film cut from a raw material film (for example, from thepolyvinyl alcohol-based film or from the polymer film) to have apredetermined size, and the sheet-to-roll process may be performedthrough a method in which as a portion of raw material films, a rolltype film in which an elongated film is wound is used, and as theremaining raw material film thereof, a sheet-fed type film cut to have apredetermined size is used. In addition, the roll-to-roll process may beperformed through a method in which a roll type film is used as a rawmaterial film. In consideration of continuity and productivity in theprocess, the roll-to-roll process may be used among the processesdescribed above.

For example, the method of manufacturing a thin film polarizer accordingto an exemplary embodiment of the present disclosure may include forminga film laminate including two or more non-oriented polymer films and twoor more non-oriented polyvinyl alcohol-based films by alternatelyarraying non-oriented polymer film rolls and non-oriented polyvinylalcohol-based film rolls and alternating bonding the polyvinylalcohol-based film and the polymer film to each other using attractiveforce or an adhesive layer while unwinding the polyvinyl alcohol-basedfilm and the polymer film from the film rolls; orienting the filmlaminate so that the polyvinyl alcohol-based film provided after theorientation process has a thickness of 10 μm or less; and separating thepolymer films and the polyvinyl alcohol-based films of the oriented filmlaminate from each other.

After the two or more non-oriented polymer films and the two or morenon-oriented polyvinyl alcohol-based films are bonded to each other, are-winding process thereof may also be performed such that the bondedfilm may be rewound in the form of a roll and the film laminate may beunwound from the re-wound film laminate roll so as to be introduced inan orientation process, or an orientation process thereof may beimmediately performed without a re-winding process.

In addition, the separation process may be performed through a method ofinserting a delaminating unit (for example, a delamination roll) betweenthe polymer film and the polyvinyl alcohol-based film so as to separatethe polymer film from the polyvinyl alcohol-based film at an interfacetherebetween and winding the separated polymer film and polyvinylalcohol-based film around different rolls, respectively.

The polarizer of the present disclosure manufactured through the methodas described above may have a significantly thin thickness of 10 μm orless, in detail, around 1 μm to 10 μm, in further detail, around 3 μm to10 μm. In addition, even in the case of such a thin thickness, polarizergroup transmittance may be in a range of around 40 to 45% and a degreeof polarization may be 99% or more, whereby significantly excellentphysical optical properties may be exhibited.

In addition, the polarizer according to an exemplary embodiment of thepresent disclosure may have significantly excellent uniformity in thedegree of polarization in a width direction of the polarizer. In detail,in the case of the polarizer according to an exemplary embodiment of thepresent disclosure, a standard deviation with respect to a degree ofpolarization, measured at ten points spaced apart from one another atequidistant intervals in the width direction of the polarizer, may be0.002% or less.

On the other hand, a polarizing plate may be formed by stacking atransparent film on one surface or both surfaces of a polarizeraccording to an exemplary embodiment of the present disclosure asdescribed above. In this case, as the transparent film, various filmscommonly used as a polarizer protective film or a retardation film maybe used without particular limitation. For example, the transparent filmsuch as an acrylic film, a polyethylene terephthalate film, apolyethylene terephthalate film treated with an acrylic primer, acellulose-based film, a cyclic olefin-based film, a polycarbonate-basedfilm, a polynorbornene-based film, and the like, may be used.

A method of stacking a polarizer and a transparent film on each other isnot particularly limited and may be performed using a commonly knownadhesive or cohesive agent, or the like. Here, the cohesive adhesive orthe adhesive may be appropriately selected depending on a material ofthe transparent film, and the like. For example, when thecellulose-based film is used as the transparent film, a water-basedadhesive such as a polyvinyl alcohol-based adhesive may be used, andwhen the acrylic film, the cyclic olefin-based film or the like is usedas the transparent film, a photocurable adhesive or a thermosettingadhesive such as an acrylic adhesive or an epoxy-based adhesive may beused.

Although the method of stacking a polarizer and a transparent film oneach other is not particularly limited, a roll-to-roll scheme using apolarizer film roll and a transparent film roll may be used in terms ofproductivity. Since the method of manufacturing a polarizing plate bystacking a polarizer and a transparent film on each other through theroll-to-roll scheme is a commonly used method, a detailed descriptionthereof will be omitted. In a case in which the polarizing plate ismanufactured through the roll-to-roll scheme, an elongated roll-typepolarizing plate may be obtained.

In addition to the transparent film, the polarizing plate according toan exemplary embodiment of the present disclosure may further include adifferent functional optical layer such as a brightness improvementfilm, a primer layer, a hard coating layer, a glare proof layer, anantireflective layer, or a cohesive layer for adhesion to a liquidcrystal panel, and the like. A method of forming the optical layer isnot particularly limited, and a commonly known method may be used.

The polarizing plate according to an exemplary embodiment of the presentdisclosure may have excellent optical properties while having asignificantly reduced thickness as compared to that of a polarizingplate according to the related art, so as to be usefully used fordisplay devices such as a liquid crystal display panel, an organicelectroluminescence device, and the like.

Mode for Embodiments of Invention

Hereinafter, the present disclosure will be described in further detail,based on the following embodiments.

Embodiment 1

Three sheets of non-oriented polyvinyl alcohol-based film and two sheetsof non-oriented polyurethane film were alternately stacked on each otherwithout using a medium material to thus form a non-oriented filmlaminate having a structure of a non-oriented polyvinyl alcohol-basedfilm/a non-oriented polyurethane film/a non-oriented polyvinylalcohol-based film/a non-oriented polyurethane film/a non-orientedpolyvinyl alcohol-based film.

In this case, as the non-oriented polyvinyl alcohol-based film, a PE30grade polyvinyl alcohol-based film (thickness: 30 μm) by Kuraray wasused, and swelled in a pure solution at 25° C. for 15 seconds and wasthen subjected to a dyeing process performed using an iodine solutionhaving a concentration of 0.3 wt % at a temperature of 25° C. for 60seconds.

On the other hand, as the non-oriented polyurethane film, a filmmanufactured using a thermoplastic polyurethane resin obtained byreacting methylene diphenyl diisocyanate, 1,4-butandiol, and adipic acidwith each other, was used.

The non-oriented film laminate was subjected to the cleaning process ina solution having 1 wt % of boron for 15 seconds, and the film laminatewas then oriented at an orientation magnification of 7 times, in asolution including 2.5 wt % of boron at 52° C. After the orientationprocess was carried out, a complementary process was performed using 5wt % of a potassium iodide (KI) solution, and the film laminate was thendried in an oven of 80° C. for five minutes. Then, three sheets of thinfilm polarizers having a thickness of 5 to 8 μm were obtained byseparating the polyurethane film from the polyvinyl alcohol-based filmthrough peel strength of 0.5N/2 cm.

Embodiment 2

Two sheets of non-oriented polyvinyl alcohol-based film and two sheetsof non-oriented polyurethane film were alternately stacked on each otherwithout using a medium material, and two sheets of thin film polarizershaving a thickness of 5 to 7 μm were obtained through the same method asthat of Embodiment 1, except that a non-oriented film laminate having astructure of a non-oriented polyvinyl alcohol-based film/a non-orientedpolyurethane film/a non-oriented polyvinyl alcohol-based film/anon-oriented polyurethane film is formed.

Embodiment 3

4 wt % of an aqueous solution was produced by dissolving polyvinylalcohol (an average degree of polymerization of 2000, a degree ofsaponification of 94%, By Nippon Gohsei) containing an acetoacetyl group(5 wt %) in pure water. Here, 6.7 parts by weight of a titanium aminecomplex crosslinking agent (TYZOR TE by Dupont) with respect to 100parts by weight of polyvinyl alcohol was added and stirred to be mixedso as to manufacture adhesive A.

The adhesive A was coated on both surfaces of a non-orientedpolyurethane film to a thickness of 100 nm, and two sheets ofnon-oriented polyvinyl alcohol-based film were then bonded thereto tomanufacture a film laminate 1 having a structure of a non-orientedpolyvinyl alcohol-based film/a non-oriented polyurethane film/anon-oriented polyvinyl alcohol-based film. The adhesive A was coated onone surface of another non-oriented polyurethane film to a thickness of100 nm, and one sheet of non-oriented polyvinyl alcohol-based film wasthen bonded thereto to manufacture a film laminate 2 having a structureof a non-oriented polyurethane film/a non-oriented polyvinylalcohol-based film. Then, the film laminate 1 and the film laminate 2swelled in a pure solution at 25° C. for 15 seconds, and were thensubjected to a dyeing process performed using an iodine solution havinga concentration of 0.3 wt % at a temperature of 25° C. for 60 seconds.

In this case, as the non-oriented polyvinyl alcohol-based film, an M2000grade polyvinyl alcohol-based film (thickness: 20 μm) by Nippon Gohseiwas used, and as the non-oriented polyurethane film, a film manufacturedusing a thermoplastic polyurethane resin obtained by reacting methylenediphenyl diisocyanate, 1,4-butandiol, and adipic acid with each other,was used.

Then, the film laminate 1 and the film laminate 2 were bonded to eachother through attractive force to thus form a non-oriented film laminatehaving a structure of a non-oriented polyvinyl alcohol-based film/anon-oriented polyurethane film/a non-oriented polyvinyl alcohol-basedfilm/a non-oriented polyurethane film/a non-oriented polyvinylalcohol-based film.

The non-oriented film laminate was subjected to a cleaning process in asolution having 1 wt % of boron for 15 seconds, and the film laminatewas then oriented at an orientation magnification of 7 times, in asolution including 2.5 wt % of boron at 52° C. After the orientationprocess was carried out, a complementary process was performed using 5wt % of a potassium iodide (KI) solution, and the film laminate was thendried in an oven of 80° C. for five minutes. Then, three sheets of thinfilm polarizers having a thickness of 5 to 8 μm were obtained byseparating the polyurethane film from the polyvinyl alcohol-based filmthrough peel strength of 0.7N/2 cm.

COMPARATIVE EXAMPLE 1

A PVA aqueous solution was formed by dissolving a PVA (an M-grade PVApowder by Nippon Gohsei, an average degree of polymerization of 2400, anaverage degree of saponification of 99 mol %) in pure water at 100° C.,and a corona treatment was then performed on a PET (NOVA-Clear SG007grade by MGC) having a thickness of 200 μm to subsequently be coatedusing a lip coater and then be dried in an oven of 80° C. for 10minutes, such that the film laminate was formed. In this case, athickness of a coated PVA film was 10 μm. The film laminate wassubjected to a swelling process performed using a pure solution at 25°C. for 15 seconds, and then subjected to a dyeing process performedusing an iodine solution having a concentration of 0.3 wt % at atemperature of 25° C. for 60 seconds. Whereby, a non-oriented filmlaminate was formed.

Subsequently, the non-oriented film laminate was subjected to thecleaning process in a solution having 1 wt % of boron at 25° C. for 15seconds and then subjected to a 5.5 times orientation process in asolution including 2.5 wt % of boron at 52° C. After the orientationprocess was carried out, a complementary process was performed using 5wt % of a KI solution, and the film laminate was then dried in an ovenof 80° C. for five minutes. Then, a thin film PVA film having athickness of 4 to 4.5 μm was obtained by separating a PET film from thePVA film.

COMPARATIVE EXAMPLE 2

Non-oriented polyvinyl alcohol-based films were bonded to both surfacesof a non-oriented polyurethane film without using a medium material, anda non-oriented film laminate having a structure of a non-orientedpolyvinyl alcohol-based film/a non-oriented polyurethane film/anon-oriented polyvinyl alcohol-based film was formed. As thenon-oriented polyvinyl alcohol-based film and the non-orientedpolyurethane film, the same ones as those of Embodiment 1 were used.

After the non-oriented film laminate was subjected to a cleaning processin a solution having 1 wt % of boron for 15 seconds, the film laminatewas oriented at an orientation magnification of 7 times, in a solutionincluding 2.5 wt % of boron at 52° C. After the orientation process wascarried out, a complementary process was performed using 5 wt % of apotassium iodide (KI) solution, and the film laminate was then dried inan oven of 80° C. for five minutes. Then, two sheets of thin filmpolarizers having a thickness of 7.5 μm were obtained by separating thepolyurethane film from the polyvinyl alcohol-based film.

EXPERIMENTAL EXAMPLE 1 Evaluation of Surface Properties

A surface state of the film laminate completed in the orientation anddrying processes in Embodiment 1 and a surface state of the filmlaminate completed in the orientation and drying processes inComparative Example 1 were observed with the naked eye. FIG. 2illustrates a surface state of the film laminate of Embodiment 1, andFIG. 3 illustrates a surface state of the film laminate of ComparativeExample 1.

As illustrated in FIGS. 2 and 3, in the case of the film laminate ofEmbodiment 1, a PVA film surface state after the orientation and dryingprocesses is uniform and good, while in the case of the film laminate ofComparative Example 1, a film surface is not uniform and is partiallypeeled off in places.

EXPERIMENTAL EXAMPLE 2 Measurement of Maximum Orientation Magnification

Maximum orientation magnifications of the non-oriented film laminatesmanufactured in Embodiments 1 to 3 and Comparative Examples 1 and 2 weremeasured by increasing the orientation magnification to an orientationmagnification of two or more times, respectively, until breakage occurs.Here, the maximum orientation magnification refers to an orientationmagnification immediately before breakage occurs.

The orientation process was performed using two methods of a dryorientation process at 25° C. and a wet orientation process performed ina boron aqueous solution having 2 wt % of boron concentration. Resultsthereof are as illustrated in the following [Table 1].

TABLE 1 Maximum Draw Ratio Wet Orientation Classification DryOrientation (25° C.) (55° C., 2 wt % of Boron) Embodiment 1 9.0 Times11.5 Times Embodiment 2 8.5 Times 10.7 Times Embodiment 3 9.0 Times 11.5Times Comparative 4.0 Times  5.5 Times Example 1 Comparative 8.3 Times 9.0 Times Example 2

As illustrated in [Table 1] above, it can be appreciated that the filmlaminates of Embodiments 1 to 3 according to the present disclosure havesignificantly excellent maximum draw ratios as compared to the filmlaminates of Comparative Examples 1 and 3, and these results indicatethat a breakage occurrence rate under the same condition as each otheris relatively low. In detail, in the case of the wet orientationprocess, a high-magnification orientation of 10 times or more may beobtained in the film laminates of Embodiments 1 to 3 so as to besignificantly advantageous for manufacturing a thin film polarizer.

EXPERIMENTAL EXAMPLE 3 Physical Properties of Thin Film Polarizer

In the case of the thin film polarizers manufactured according toEmbodiments 1 to 3 and Comparative Examples 1 and 3, optical propertiessuch as polarizer group transmittances, degrees of polarization,polarizer group colors, orthogonal colors, and the like were measuredusing JASCO V-7100 Spectrophotometer, and measurement results thereofare provided in the following [Table 2]. In the following [Table 2], anexternal polarizer may refer to a polarizer stacked on an externalsurface of a film laminate, and an internal polarizer may refer to apolarizer disposed between polymer films.

TABLE 2 Single Degree Trans- of Single Cross mittance Polarization ColorColor Classification (%) (%) a b a b Embod- External 40.59 99.9865 −0.451.89 0.85 −1.60 iment Polarizer 1 Internal 41.75 99.8491 −0.91 1.38 1.21−2.65 Polarizer Embod- External 40.66 99.9854 −0.51 1.81 0.83 −1.69iment 2 Polarizer Internal 42.01 99.8452 −0.95 1.25 1.32 −2.77 PolarizerEmbod- External 40.80 99.9894 −0.65 1.98 0.73 −1.58 iment 3 PolarizerInternal 42.34 99.8413 −0.84 1.21 1.39 −2.85 Polarizer Comparative 33.2298.5009 2.23 0.52 6.09 −3.72 Example 1 Comparative 40.48 99.9837 −0.481.75 0.87 −1.50 Example 2

In the case of the thin film polarizers manufactured in Embodiments 1 to3 according to the method of the present disclosure with reference to[Table 2] above, it can be appreciated that optical properties such aspolarizer single Transmittances, degrees of polarization, color sense,and the like are excellent as compared to the polarizers manufactured inComparative Examples 1 and 2.

[Description of Reference Characters]

-   H: Holder-   A: Polyvinyl Alcohol-based Film-   B: Polymer Film-   MD: Longitudinal Orientation Direction

The invention claimed is:
 1. A method of manufacturing a thin filmpolarizer, comprising: forming a film laminate by alternately bondingtwo or more non-oriented polymer films and two or more non-orientedpolyvinyl alcohol-based films to each other using attractive force or anadhesive layer; orienting the film laminate so that the polyvinylalcohol-based film has a thickness of 10 μm or less after the orientingof the film laminate; and separating the polymer films and the polyvinylalcohol-based films of the oriented film laminate from each other. 2.The method of claim 1, wherein the film laminate comprises a firstnon-oriented polyvinyl alcohol-based film, a first non-oriented polymerfilm bonded to the first non-oriented polyvinyl alcohol-based film, asecond non-oriented polyvinyl alcohol-based film bonded to the firstnon-oriented polymer film, and a second non-oriented polymer filmstacked on the second non-oriented polyvinyl alcohol-based film.
 3. Themethod of claim 1, wherein the film laminate comprises a firstnon-oriented polyvinyl alcohol-based film, a first non-oriented polymerfilm bonded to the first non-oriented polyvinyl alcohol-based film, asecond non-oriented polyvinyl alcohol-based film bonded to the firstnon-oriented polymer film, a second non-oriented polymer film bonded tothe second non-oriented polyvinyl alcohol-based film, and a thirdnon-oriented polyvinyl alcohol-based film bonded to the secondnon-oriented polymer film.
 4. The method of claim 1, wherein thenon-oriented polymer film is a polymer film having a maximum orientationmagnification of five or more times.
 5. The method of claim 1, whereinthe non-oriented polymer film is one or more selected from a groupincluding a low-density polyethylene resin, a high-density polyethyleneresin, a copolymer resin containing ethylene vinyl acetate inhigh-density polyethylene, a polypropylene resin, a polyurethane resin,a polyethylene terephthalate resin containing isophtalic acid, awatersoluble cellulose resin, and an acrylic resin.
 6. The method ofclaim 1, wherein the orienting of the film laminate is performed throughdry orientation or wet orientation.
 7. The method of claim 1, whereinthe orienting of the film laminate is performed at a temperature of 20°C. to 85° C. at an orientation magnification of 5 to 15 times.
 8. Themethod of claim 1, wherein the orienting of the film laminate isperformed in a boron aqueous solution having a boron concentrationranging from 1 to 5 wt %.
 9. The method of claim 1, further comprisingdyeing the non-oriented polyvinyl alcohol-based film with at least oneof iodine and dichroic dye before the orienting of the film laminate.10. The method of claim 1, wherein adhesion between the orientedpolyvinyl alcohol-based film and the oriented polymer film after theorienting of the film laminate is 2N/2 cm or less.
 11. The method ofclaim 1, wherein the separating of the polymer film from the polyvinylalcohol-based film in the oriented film laminate is performed byapplying 2N/2 cm or less of peel strength.
 12. A thin film polarizerbeing manufactured through the method of claim 1, having a thickness of10 μm or less, group transmittance of 40 to 45%, and a degree ofpolarization of 99% or more.
 13. The thin film polarizer of claim 12,wherein in the thin film polarizer, a standard deviation with respect toa degree of polarization measured at 10 points positioned to have anequidistant interval between the points in a width direction of the thinfilm polarizer is
 0. 002% or less.
 14. A polarizing plate comprising thethin film polarizer of claim
 12. 15. A display device comprising thepolarizing plate of claim 14.